resolv: Switch to android-base/logging.h

This moves us away from async_safe_format_log() so we can drop the
last remaining dependency on internal bionic headers.

The debug logging code has bitrotten for a very long time and didn't
even compile any more, and when it finally did I noticed that
dump_answer() was trying to create a temporary file in /data on each
cache insert! Plenty of room for future improvements.

Test: m netd_integration_test
Test: build with kVerboseLogging=true in all modules and check logcat
Change-Id: I5d8c4b207f1477e75476b06b863a7d1723664407